This circuit is intended to signal through a flashing LED, the exceeding of a fixed threshold in room noise, chosen from three fixed levels, namely 50, 70 and 85 dB. Two Op-amps provide the necessary circuit gain for sounds picked-up by a miniature electret microphone to drive a LED.
Authored by
at
, Added: 19 Jul 2007
http://www.electronics-lab.com/projects/sensors/012/
